Tyk2-IN-3 is very potent Tyk2 pseudokinase against (99% inhibition at 1 μM) but lacks potency against all other kinases in the kinome assay panel except IKK (96% inhibition) and the JAK1 pseudokinase domain (99% inhibition at 1 μM). The pseudokinase domains of JAK2 and JAK3 are not part of the kinome screening panel. In the IL-23-stimulated kit225 T cell assay, Tyk2-IN-3 inhibits the stimulated response with an IC50 of 485±143 nM (n=3).